QUANTUM-FIELD THEORY OF METALLIC SPIN-GLASSES

We introduce an effective field theory for the vicinity of a zero-temp erature quantum transition between a metallic spin glass (''spin-densi ty glass'') and a metallic quantum paramagnet. Following a mean-field analysis, we perform a perturbative renormalization-group study and fi nd that the critical properties are dominated by static disorder-induc ed fluctuations, and that dynamic quantum-mechanical effects are dange rously irrelevant. A Gaussian fixed point is stable for a finite range of couplings for spatial dimensionality d > 8, but disorder effects a lways lead to runaway hows to strong coupling for d less than or equal to 8. Scaling hypotheses for a static strong-coupling critical field theory are proposed. The nonlinear susceptibility has an anomalously w eak singularity at such a critical point. Although motivated by a pert urbative study of metallic spin glasses, the scaling hypotheses are mo re general, and could apply to other quantum spin glass to paramagnet transitions.